Flash guard for dynamo-electric machines



Mar. 13, 1923. 1,448,419

- M. w. SMITH FLASH GUARD FOR DYNAMO ELECTRIC MACHINES Filed May 14, 1920 WITNESSES: INVENTOR ,7

' Mary/h W. 3/77/77? 62W Patented Mar. 13, 1923.

UNITED STATES PATENT OFF-ICE.

MARVIN W. SMITH, 0F WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

FLASH GUARD FOR DYNAMIC-ELECTRIC 'MACHINES.

Application filed May 14,

To all to from it may concern Be it known that I, MARVIN WV. SMITH, a citizen of the United States, and a resident of Vilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful 1m rovement in Flash Guards for Dynamo- *lectric Machines, of which the following is a specification.

My invention relates to dynamo-electric machines of the commutator type and it has particular relation to means for protecting the commutator cylinders and the bearing pedestals Off machines of the character indicated from flash-overs or arcing between the commutator cylinder and other portions of the machine of different potential.

The object of my invention is to provide a flash guard or barrier that shall prevent flashing-over between the commutator cylinder and the bearing pedestal, that shall be free from carbonization, of simple design, be relatively inexpensive to construct and of great durability and that shall permit free access to the commutator for the purposes of inspection and repair.

It has been customary, in the construction of dynamoelectric machines, to provide flash guards of circular contour that encircle one or bot-h ends of the commutator and to mount screens or other barriers thereon in close proximity to the commutator cylinder and between adjacent sets of brushes for preventing arcing therebetween. Such construction did not prevent fiashing and, as the arcs were partially confined by the guards, they tended to become explosive and to force the arcs to portions of the machine which they would not otherwise reach. After arcing has occurred a number of times, the guards become carbonized and coated with metal particles, by reason of their proximity to the commutator cylinder and brushes thus rendering them partially conducting and, therefore, productive of arcing, even when the machine is operated at no load or at normal voltage.

By my invention, I provide an end pedestal of a dynamo-electric machine with a flash guard that is so removed from the commutator and co-operating brushes that repeated arcing does not impair the insulating property thereof.

Briefly speaking, my invention consists of mounting an annular guard composed of in- 1920. Serial No. 381,261.

sulating material between the commutator and the adjacent bearing pedestal and as far removed as possible from the source of arcing.

F or a better understanding of my invention, reference may now be had to the accompanying drawing, which consists of a single figure illustrating a view, in side elevation, of a dynamo-electric machine provided with a flash guard constructed in accordance with my invention.

A synchronous converter 1 is illustrated as embodying my invention, but the invention is applicable to any type of dynamoelectric machine receiving or delivering direct current. The machine comprises a stator frame 2, a rotor 3, a base plate Land bearing pedestals 5 and 6 at the respective ends of the machine. The rotor 3 comprises an armature 7, a commutator cylinder 8 and a set of collector rings 9 positioned upon a shaft 10, which is rotatably mounted upon bearings 11 and 12 of the pedestals 5 and 6, respectively. Sets of brushes 13 are mounted upon an annular insulating support 14:, secured to the stator frame 2 in any suitable manner.

An annular flash guard or barrier 15, made of some suitable insulating material, such, for example, as asbestos lumber, is provided with an offset collar portion 16 by which it is mounted upon the bearing 11 of the pedestal 5 opposite the commutator cylinder 8 and the brushes 13. Thus, the guard 15 is disposed at a considerable distance from the commutator cylinder, which prevents it from being burned and thereby carbonized and from having particles of carbon or copper deposited thereon by the arcs.

Upon an overload or an increase in voltage there is a tendency for an arc to form between the end of the commutator cylinder and the nearest portion of the bearing pedestal, which is held at ground potential. The shield 15 covers the entire inner surface of the bearing pedestal 5, and a portion 17 of the collar member 16 extends between the innermost portion of the pedestal 5 and the commutator cylinder 8. The guard 15 may be made in any one of various shapes, but it should be of suflicient size to prevent arcs from flashing around it and be constructed in such a manner as to permit of its being easily removed.

From the foregoing description, it will be apparent to those skilled in the art that, by my invention, 1 have provided a structure which greatly reduces the flashing-over and arcing in a dynamo-electric machine, and which is relatively simple and inexpensive to manufacture and to maintain and may be readily installed or removed.

While I have shown my invention in a preferred form, it may be subject to minor modifications without departing from the spirt thereof; therefore, I desire to be limited only by the scope of the appended claims.

I claim as my invention:

1. In a dynamo-electric machine, the combination with a commutator cylinder mounted upon a shaft, brushes co-operating with said commutator cylinder and a bearing pedestal for supporting said commutator shaft, of means for insulating said pedestal from said commutator cylinder comprising an annular barrier carried by said pedestal.

2. In a dynamo-electric machine, the combination with a commutator cylinder mounted upon a shaft, brushes co-operating with said cylinder and a bearing pedestal for supporting said commutator shaft, of a flash guard mounted on said bearing pedestal.

3. In a dynamo-electric machine, the combination with a commutator cylinder mount ed upon a shaft, brushes co-operating With said cylinder and a bearing pedestal for supporting said commutator shaft, of a flash guard so positioned between said pedestal and said commutator as to be relatively adjacent said pedestal and relatively remote from said commutator.

4. In a dynamo-electric machine, the combination with a commutator cylinder mounted upon a rotatable shaft, brushes co-operating with said commutator cylinder, and, a pedestal provided with a bearing for supporting said shaft, of a flash guard securely mounted upon said bearing and secured to said pedestal.

In a dynamo-electric machine, the combination with a commutator cylinder mounted upon a rotatable shaft, brushes co-operating with said commutator cylinder, and a pedestal provided with a bearing for supporting said shaft, of a flash guard for said pedestal mounted upon said bearing and provided with an annular collar substantially covering the end of said bearing adjacent said commutator.

6. In a dynamo electric machine, the combination with a commutatorcylinder mounted upon a shaft, brushes co-operating with said cylinder, a bearing pedestal having a bearing for supporting said commutator shaft, of means for preventing arcing to said pedestal comprising a barrier carried by said pedestal and provided with an offset hub portion adapted to partially enclose said bearing.

7. In a dynamo-electric machine, the combination with a commutator cylinder mounted upon a shaft, brushes co-operating with said cylinder and bearin pedestal for supporting said commutator shaft, of a housing composed of insulating material encasing the side of said pedestal adjacent said commutator cylinder.

In testimony whereof, I have hereunto subscribed my name this 4th day of May,

MARVIN W. SMITH. 

